This disclosure relates to position sensing. There are many situations in which it is desirable to sense the position of one or more relatively moveable portions of an assembly. One example is a machine tool in which a moveable member such as a tool needs to be precisely positioned relative to a fixed member such as the workpiece or a table. Other examples include active suspension systems for vehicles or portions of vehicles that are subject to random accelerations, particularly as the vehicle moves. For active suspension systems to be effective, the position of the moveable portion of the assembly must be known.